Hitherto, a measurement method has been used in which to analyze characteristics of a substance, a specimen is held on an aperture array structure, an electromagnetic wave is applied to the aperture array structure on which the specimen has been held, and a transmission spectrum or the like thereof is analyzed to detect characteristics of the specimen. A specific example thereof is a method of applying a terahertz wave to a specimen, such as a protein, attached to a metal mesh, and analyzing a transmission spectrum thereof.
As an existing technique which is such a method of analyzing a transmission spectrum using an electromagnetic wave, for example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2007-010366) discloses a method of applying an electromagnetic wave toward an aperture array structure (e.g., a mesh-shaped conductive plate) on which a specimen has been held, measuring the electromagnetic wave having passed through the aperture array structure, and detecting characteristics of the specimen on the basis of a change in frequency characteristics of a measured value, the change being caused by the presence of the specimen.
In the aperture array structure disclosed in Patent Document 1, from the description of FIG. 18(b) and the like, the opening area of each aperture at the front side is basically substantially the same as that at the back side, the angle formed between an inner wall surface forming each aperture and a principal surface of the aperture array structure is assumed as substantially 90 degrees.
In such a case, if the amount of a specimen is small, a change in frequency characteristics is slight, and detection is difficult. Thus, provision of a measurement device for realizing measurement with excellent measurement sensitivity is still desired.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2007-010366